What kind of key mechanism does it have (usual cylinder with pins or tubular key or...)? Masterlock is known for fitting the lock cylinder with straight, smooth pins (the cheapest ones), and some people can pick them faster than they can open the package containing a padlock. Locks not intended for high security applications (as the one in question), may be specially insecure. I would suggest calling a locksmith (if you don't want to spend the time to learn to pick locks yourself).
– k-lJan 16 '17 at 2:29

It's a tubular opening like a kryptonite lock, but made a few generations after the Bic pen cap trick. The guy that picked it used 2 tools, he wedged the circle down then manipulated the mechanism around.
– WebsterJan 16 '17 at 3:02

1

Likely not to work but almost free, cut a bit of cardboard and bend it into a tube, press the tube into the opening of the lock and turn, as if it was a kryptonite key. (It did work on a long series of expensive bike locks.)
– WillekeJan 16 '17 at 20:38

7 Answers
7

You need a short hook and a bogota lockpick. Master locks are so incredibly poorly manufacured that it typically takes 30-60 seconds to open one you don't know. Sparrows sells decent picks, but buy some cheaper used picks on eBay. For torque, you can take a generic windshield wiper insert and bend it 90° with a pair of pliers.

A snapgun would work, but only if the keyway isn't too tight.

Look at bosnianbill's videos on youtube.

Edit: looked again, it appears to be a tubular cylinder. You need a short and medium hook for those, and a specific tension wrench for tubular locks. Sparrows sells these. Pick it three times in a star pattern, it will open. They are more inconvenient to pick than difficult. If you want it to be very simple it will cost you more, but requires no skill. See e.g. http://www.lockpicks.com/8-pin-advanced-tubular-pick.html
Ask their support staff what kind of pick you need for this lock.

In some U.S. states possession equals criminal intent, but I've never heard of anyone being fined for that. OP is doing this in the bedroom anyway. His romantic handcuffs are much nicer than the regular kind, although they can be bypassed easily.
– user400344Jan 31 '17 at 12:33

If they use a ratchet type of closing (like a hook/sheer that latches) there's a really good "drinks can" hack that you may be able to try similar to this How to make a Simple Lock Shim

Edit in response to Willeke's comment.

The basic process involves cutting and shaping a thin, sturdy, sheet of metal (a shim); which can be obtained "carefully" from cutting an aluminium drinks can, you can also buy shim from engineering suppliers/online; these are normally made of brass and may be too soft for some locks (the same with aluminium). If you find these metals are too soft, try some steel shim instead. Be aware, these metals aren't kind on ordinary scissors...

The premise is that you cut the shim to size, and then shape it accordingly so it can slide inside the opening between the bar that goes into where the locking mechanism is, and, the case that houses it. With enough force (care with sharp edges), the shim slides between the "bolt"/"sheer pin" (sometimes a ball-bearing), that is part of the lock internals, and between the movable bar that allows you to open and close the lock around things.

This is much harder to describe than picture :D

If this works with those cuffs... I've never "reverse engineered" them before...

There are also other items you can use to slide between the housing and the movable locking bar depending upon the type of lock you have. Being unable to see the type or style of lock that's in the Questioners' post, I am unable to determine the best route to take. However, ZipLock ties, (plasticuffs), and old style handcuffs can be bypassed in a similar fashion by sliding something between the "sheer" and the ratchet-shaped surface.

Some items include:

Sparkplug shims (they are quite handy as they come in many thicknesses, however they may be destroyed when using them for something like this)

Padlock Shims - often sold in packs of several sizes from locksmiths, these can be reshaped fairly easily with a file and some wet or dry sand-paper; they can also be repurposed for different lock types

Old-style metal sweet tins. However they can be quite thick; although these could be thinned using wet or dry sand-paper and some elbow-grease.

Other than that, I would recommend a "Junior Hacksaw". or a "mini-hacksaw" like this pictured: "Mini-Hacksaw"
(ok, apparently I need 10 rep to post more than two links!)Thanks for the rep :) )

And! Hold the lock as sturdy as possible with an adjustable wrench, like this one, you want all that arm energy going into the cut, not moving everything about :P : "Adjustable Wrench"

Edit: I have been a hobby lock-picker for years. The time and effort involved in sourcing picks and trying to learn without breaking a lock, or breaking/damaging a cheap pick (I use Southord), you might as well just hacksaw it off considering hacksaws are cheap in comparison. Depends how much the cuffs were? but yes, time and effort, go for a hacksaw if it can't be shimmed...

Can you please copy or describe information from your link to your answer? People do like to know whether clicking a link is going to be useful and if your link dies your answer will be useful without the extra information.
– WillekeApr 14 '17 at 18:26

@Willeke - No worries! I can do that :) May take me a little while to do it, but I will make a start.
– TimelessApr 15 '17 at 13:40

Did you see the comments on the answer given by Topher Brink on this question, where it is stated that this lock is a "tubular cylinder", which can't be shimmed? This kind of renders your entire answer useless for the OP.
– holroyApr 15 '17 at 17:16

@Timeless, thanks, that is a real answer. (Even though it seems to miss the point as is pointed out in the other comment.)
– WillekeApr 15 '17 at 19:55

My experience (using and repairing these tools on a daily basis) is that a $20 angle grinder from Harbor Freight with a "slicing wheel" mounted is far easier to hold steady than a (usually more expensive) rotary tool, and either one will require a second person to steady the lock. However, the big problem with any powered abrasive cutter is the shower of sparks the wheel will throw.

An option that will still deposit abrasive particles and metal filings near the cut, but at least won't throw them across the room after igniting them (and hence possibly start a fire in bedclothes, curtains, etc.) is a "rod saw" or tile cutting blade mounted in a hacksaw frame. These carbide abrasive blades will cut nearly anything (including glass and tile, and surely including the lock's shackle), but being muscle powered won't heat the filings from the shackle to ignition. Yes, it'll take a long time to cut through a hard shackle this way -- but this will do the least damage to the bedroom.

One additional advantage of a rod saw or abrasive edge hacksaw blade is that the cuttings won't come out of the cut at high velocity. Temperature aside, this would absolutely required eye protection be worn by everyone assisting in the operation. Such protection is a good idea, but not a fast requirement, with a low speed abrasive cutter like a rod saw.

Small rotary tools are difficult to hold steady enough for this kind of cut, and lack the power to handle a deep cut with a large enough wheel for the thickness of this lock's shackle. A tool getting loose can cause serious injury, as can a wheel that shatters after binding in the cut.
– Zeiss IkonJan 16 '17 at 12:20

My experience is that the tool with a small cutoff wheels, 5 cm or smaller is easy to manipulate and can be held in the "precision grip". Larger, air powered high-speed tools are indeed more powerful and likely to go astray. As with any tool, safety goggles are advisable.
– DrMoishe PippikJan 16 '17 at 20:49

I can't see them well enough or know how the lock works to be certain but could you use a shim? This is a little bit of metal (cut from a drink can) that you can slide between the pin that holds the cuff closed and the cuff. Something like this: https://www.youtube.com/watch?v=PC-1S4cHUPs

We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

Locks like the Street Cuff are intentionally made resistant to bolt cutters.
– Zeiss IkonJan 16 '17 at 18:46